package demo;

/**
 * Created with IntelliJ IDEA.
 * Description:
 * User: WHY
 * Date: 2022-10-11
 * Time: 12:01
 */
import java.util.Scanner;

// 注意类名必须为 Main, 不要有任何 package xxx 信息
public class TestDemo1 {
    public static void main(String[] args) {
        Scanner scanner =new Scanner(System.in);
        String s=scanner.nextLine();
        int low=0;
        int high=s.length()-1;
        int a=s.charAt(low);
        int b=s.charAt(high);
        String s1=null;
        while(low<high){
            a=b;
            a++;
            b--;

        }
        System.out.println(s1);

    }

}